San Francisco (CNN Business)Ford is investigating the testing procedures it uses to certify its fuel economy and emissions standards after employees raised concerns about potential inaccuracies.

It has hired an outside firm to look into the testing process the company said in a statement on Thursday.

Ford has also brought on independent experts and will be using an outside lab throughout the investigation.

Ford has already identified potential concerns with how it calculates road load, which is the force on a vehicle while driving at a constant speed over a smooth and level surface. The first vehicle it's investigating is the 2019 Ranger, but it will eventually test others.

Ford has voluntarily disclosed the potential issue with both the Environmental Protection Agency and the California Air Resources Board, it said.

Automakers generally do their own fuel economy testing based on strict criteria and mathematical formulas. They then report the results to the government.

The company said the investigation and potential concerns do not involve the use of so-called "defeat devices" software that can be used to cheat emissions testing.

A group of employees first raised questions about the process in September.

"At Ford, we believe that trust in our brand is earned by acting with integrity and transparency," the statement said. "As always, we strive to be transparent with our customers, employees, dealers, shareholders and other stakeholders. We understand how important it is to all audiences that we thoroughly yet swiftly complete this investigation," the statement said.

It's unclear what will come from Ford's investigation. However, other car manufacturers have had to respond to inaccurate fuel economy reporting in the past.

In 2012, the EPA found that Hyundai and Kia inadvertently overstated the fuel economy of their cars and SUVs.

As a result, they instituted a program that gives customers debit cards to make up for the extra gas they're using compared to what the fuel economy was stated when they bought their cars.